1. Related Application
This application is related to Storage Tank Level Monitoring Apparatus and Method Therefor, Ser. No. 473,144, filed Mar. 7, 1983, by John Carlin, William Mesch, Randall Thompson, Steven Beard and Tracy Stephens now U.S. Pat. No. 4,487,065 issued 12-11-84.
2. Field of the Invention
The present invention relates to a centralized system and method for monitoring and controlling oil field lease equipment and product and for securing said equipment and product against damage and theft, and, in particular, to a system and method for monitoring oil field lease equipment parameters such as storage tank levels and pumper and heater treater operation, for controlling the oil lease equipment such as diverting production when a storage tank is full, and for signaling an alarm when the theft of crude oil from a tank occurs.
3. Description of the Prior Art
For years equipment at oil field leases such as storage tanks, heater treaters, and horse-head pumpers have been monitored and maintained by personnel periodically visiting the lease. Depending on the production and size of the lease, such visits may be daily or less often. Rarely, however, are personnel stationed full time at the lease. Such personnel "manage" the lease by manually filling out various reports showing such parameters as oil levels in storage tanks, crude oil purchases from the lease, production from the wells and the like. These reports, which typically are filled out by different persons, are eventually delivered to a central location for processing. Such infrequent monitoring of the lease leads to theft of equipment, theft of crude oil, and to loss of equipment through destruction such as by fire or equipment malfunction.
The problem of crude oil theft is of special concern since for years, such theft of crude on oil leases in the United States and worldwide was generally an uncontrollable situation in the oil and gas industry. This was due, in part, to the remoteness of the oil leases and, in part, due to the undue cost in providing personnel to supervise and monitor such isolated equipment and storage tanks on a full time basis. The theft of crude oil typically occurred in fields not utilizing pipe line connections and which required the crude to be hauled out in tanker trucks. Hence, crude could be stolen by any person having access to a storage tank including truck drivers, producers, oil reclaimers, pumpers or other oil field employees. The techniques used by such thieves are numerous and varied. For example, in a typical oil field operation, a person called a gauger measures the amount of crude in a storage tank on a regular basis. If the gauger "misreads" the measurement and, for example, is off by three inches in a five hundred barrel tank, approximately eight barrels of crude are unaccounted for. The Denver Post, Volume 89, No. 228, Mar. 16, 1981, Page 1. In other cases, monthly production reports are doctored "to show a well was out of production for several days due to a mechanical malfunction while, in reality, the well continued to produce oil." Id. Also, valves on large tanks can be opened to allow crude to drain into a nearby pit and, subsequently, a vacuum truck pulls along side the pit and removes the crude. The aforesaid Denver Post article documents numerous other ways in which crude can be illegally taken from an oil lease through manipulation of the equipment or through improper record keeping pertaining to the oil lease.
Within the last ten years, and with the occurrence of a recent and severe oil and gas shortage, this critical theft problem became acute and the amount of stolen crude became considerable. It has been estimated that over $650 million dollars a year is lost alone by the Federal Government in public oil royalties to theft and accounting irregularities. Washington Crime News Services, Security Systems Digest, Feb. 10, 1982, Volume 13, No. 3, Page 8. The Federal royalty losses represent only the tip of the iceberg and estimates on the annual volume of crude oil stolen from oil field leases range from $2 billion to $6 billion dollars. Congressional Record, Dec. 14, 1982, E5115 and World Oil, March 1982, Page 5.
Traditional approaches to inhibiting crude oil thieves have been to lock and seal pipe line and tank connections, to hire armed security guards to regularly patrol the leases, and to vigorously prosecute all apprehended persons. In Texas, oil and gas producers have formed organizations such as the Texas Petroleum Industry Security Council, Inc., representing more than 10,000 independents, to develop group theft insurance plans as a measure to cope with the problem.
In a more recent approach to solving oil field thefts, tiny microdots are utilized to fingerprint oil in a particular storage tank. These microdots are typically the size of the capital "O" on a typewriter and include the name of the oil company, its lease number, its legal description, and other identifying information. Approximately 400 microdots are added to a tank of oil. In the event of theft, the proper legal authorities can obtain a sample of the oil and ascertain whether or not the oil contains microdots thereby ascertaining the true owner of the crude. The Bakersfield, California, Wednesday, May 12, 1982.
Problems comparable to the above described situation concerning crude oil theft also occur with theft of equipment, doctoring of records by personnel, malfunctioning of equipment, or losses due to disaster such as fire caused by lightening strikes and the like. No centralized, stand alone system or method for continuously monitoring and controlling the various parameters of oil lease equipment, for reporting such parameters, or for sounding an alarm when theft occurs, exists especially one adapted for the harsh environments of oil leases.
Recognizing the numerous problems associated with equipment in such remote oil leases, the inventors have developed an automated stand alone system and method for continuously monitoring and controlling oil lease equipment parameters such as crude oil production and purchase. For example, the present invention continuously measures the level of crude in the storage tanks and records production and purchase events in suitable printed tickets for use by applicable personnel and in long term computer memory for subsequent evaluation at a remote location. All such parameters are monitored by suitable transducers and processed by the system to eliminate human error in reading and recording. Furthermore, the system of the present invention is user friendly in that a human interface is provided between the system and the operator which requires a minimum amount of training. Furthermore, the system of the present invention is secure in that only authorized personnel can perform tasks with the oil lease equipment. Finally, the system of the present invention is protected from the harsh environmental conditions typically found in oil leases.
In the event of crude oil theft, the system of the present invention will detect unauthorized drops in the level of crude by means of an ultrasonic detector and signal an alarm so that proper enforcement can occur. With respect to the function of measuring oil levels in storage tanks with ultrasonic transducers, the inventors have conducted a patentability search, on their invention, the results of which follows:
______________________________________ INVENTOR U.S. Pat. No. Date Issued ______________________________________ J. D. Baird 3,553,636 Jan. 5, 1971 Austin et al 4,170,765 Oct. 9, 1979 Joseph Baumoel 4,203,324 May 20, 1980 Massa 4,210,969 July 1, 1980 Hirsch et al 4,212,201 July 15, 1980 Combs et al 4,221,004 Sept. 2, 1980 Rosie et al 4,229,798 Oct. 21, 1980 Dennis et al 4,248,087 Feb. 3, 1981 Keidel et al 4,264,788 April 28, 1981 Howard et al 4,325,255 April 20, 1982 ______________________________________
In the 1981 patent to Dennis et al (U.S. Pat. No. 4,248,087), an ultrasonic transmitting transducer and an ultrasonic receiving transducer are coupled to the external walls of the tank in which the fluid resides and whose level is to be monitored. The transducers are magnetically coupled to the side walls of the tank and are oriented so that the direction of propagation of the ultrasonic energy is normal to the fluid's surface. A microprocessor is utilized to calculate the change in fluid level in the tank and this information is then displayed. Dennis contemplated that a general purpose computer could be substituted for the microprocessor and readings from a number of tanks could be made and displayed. The section in Dennis entitled "Description of the Prior Art" provides a general discussion of known acoustic or ultrasonic measurement techniques for determining fluid levels in tanks. Three types of prior art approaches are discussed by Dennis. The first type relates to a single ultrasonic transducer located at the top of the tank (or at the bottom of the tank) which emits an energy pulse normal to the surface of the fluid to detect the fluid air interface. A second type of measurement is provided by a transmitter located near the bottom of the tank with multiple acoustical receivers mounted on the sides of the tank. A third type of system utilizes a number of echo pulses transmitted down one side of a tank in a vertical line.
The 1980 patent issued to Rosie et al (U.S. Pat. No. 4,229,798), teaches the use of an elongated tube placed at, or close to, the bottom of the tank wherein a transducer is oriented so that the ultrasonic energy wave is propagated vertically upwards inside the tube to the surface of the liquid stored in the tank. Rosie ascertains the temperature of the stored liquid in order to calculate any variations to the propagated ultrasonic energy pulse due to environmental conditions and, based upon a mathematical relationship, ascertains the true position of the fluid level in the tank. A microprocessor is then utilized to receive the temperature measurements, the ultrasonic measurements, and to visually display the results. The Rosie configuration can be utilized to issue a warning alarm when a predetermined level in the tank is reached by filling the tank with oil. It is contemplated in Rosie that for large cylindrical bulk storage tanks, the transducer sensor unit can be mounted on the side of the tank adjacent its lower end to avoid the use of a tube and, therefore, a pivoting connection must be utilized to allow the transducer to be vertically aligned.
The 1980 patent issued to Combs et al (U.S. Pat. No. 4,221,004) relates to an adjustable ultrasonic level measurement device for use in measuring the depth of flowing liquid in a channel using an ultrasonic transducer located above the channel. Temperature of the ambient air above the channel is measured and variations in the temperature are utilized to adjust the circuitry of Combs to provide for accurate ultrasonic level readings.
The 1980 patent issued to Massa (U.S. Pat. No. 4,210,969) also utilizes a microprocessor system having an ultrasonic transducer located at the top of the tank and normal to the level of the fluid for ascertaining the actual level of the fluid. In Massa, a fixed target located at a known distance from the ultrasonic transducer is utilized to take care of velocity variations caused by the presence of chemical vapors or changes in temperature. The Massa approach calibrates each reading by measuring the velocity time between the transducer and the reference target prior to the taking of a measurement.
The remaining patents developed in the patentability search set forth a variety of other techniques and approaches utilizing ultrasonic transducers and other techniques to measure the level of fluid in a tank or other apparatus. However, none of the above prior art approaches nor any of the conventional approaches currently used in the oil and gas industry to prevent or hinder theft of crude from oil storage tanks contemplates the present invention. The present invention not only includes the measurement of fluid levels in oil storage tanks but provides for an overall oil field management system that monitors tank levels and the performance of other equipment parameters. Further, it includes the generation of appropriate records and reports for the operation of the oil lease and the maintenance of a history file on each piece of equipment. The present invention also permits authorized transfers of crude from oil storage tanks into tankers, records and monitors production into the tank and shuts off a tank when full, and alerts either locally or at a remote location a suitable alarm when unauthorized transfers of crude takes place. Furthermore, the modular nature of the system of the present invention permits other monitoring and supervision of oil field equipment in addition to measuring levels in storage tanks. For example, when the flame on the heater treater goes out, for whatever reason, the event will be recorded and the gas to the line will be shut off. Or, when the sucker rod breaks on the horse head pumper, the event will be sensed, recorded, an alarm issued, and the pump turned off before it causes additional damage. The present invention is further capable of communicating with a centralized location such as the headquarters of an oil and gas company so that an operator remote from the oil lease can directly access the system.